Cutting tooth grooves of a gear or the like require specifically designed and shaped cutting tools to cut flanks of the teeth and to reach a bottom land between the teeth at the roots of the teeth.
US 2011/0255925 discloses a cutting insert for cutting tooth grooves. Several cutting inserts are removably mounted on insert seats formed in a peripheral portion of a disc shaped tool body of a cutting tool. The cutting insert includes a substantially planar insert body of a substantially square shape in a plan view. The insert body comprises two cutting edges, one each at a respective intersection ridge between each of two rake faces and an upper surface. Each cutting edge is a substantial involute in a side view of the body. Thus, involute teeth may be cut with the cutting tool and each cutting insert may be used twice, i.e. each of the two cutting edges may be used, a first cutting edge cutting a first flank of teeth when the cutting insert is positioned in an insert seat on a first side of the tool body, and a second cutting edge cutting an opposite second flank of teeth when the cutting insert is positioned in an insert seat on an opposite second side of the tool body.
In US 2012/0301233 a starting point is taken in a two-edge cutting insert to provide a side-milling cutter for machining toothing systems having an indexable cutting insert with four cutting edges that can be used in succession. The insert has a rectangular cross-section, two top surfaces facing away from each other, two long insert sides located opposite each other and also two narrow insert sides located opposite each other. Of four cutting edges of the insert, which extend along the long insert sides in the longitudinal direction, in each case two cutting edges delimit the top surfaces of the insert, each cutting edge extending in a curve. Each top surface is provided with a bearing area protruding from the top surface. By means of the bearing area, the indexable insert rests with its inactive side on the bottom of a holding pocket of the side-milling cutter. Also the narrow insert side is supported in the holding pocket. The bearing area and the narrow insert side thus, support the indexable insert relative to the holding pocket.
The curve of each cutting edge has to be adapted to the relevant tooth profile being cut with the cutting insert. Thus, in the cutting insert of US 2012/0301233 the shape and size of the bearing area is affected by a relevant curve shape of the cutting edges. For some cutting edge shapes the bearing area may be too small to provide a reliable positioning of the insert in a holding pocket during use of the side-milling cutter.
JP 2014-073545 discloses a cutting insert having a flat plate-like insert body of which the four sides can be used as cutting edges. The shape of each cutting edge forms an involute curved line. The insert body has a flat surface provided on a top face, and a flat surface provided on a lower face between two flanks on each of the top and lower faces. Each cutting edge extends along one of the flanks.